1. Field of the Invention.
This invention relates to a crystalline aluminosilicate catalyst having added silica contained within its interior structure, the manufacture of such catalyst and use thereof in the selective production of desired hydrocarbons.
2. Description of the Prior Art.
Zeolite catalysts for the disproportionation of aromatic hydrocarbons have been described by Grandio et al. in the Oil and Gas Journal, Vol. 69, No. 48 (1971). U.S. Pat. Nos. 3,126,422; 3,413,374; 3,598,878; 3,598,879 and 3,607,961 show vapor-phase disproportionation of toluene over various catalysts.
Crystalline aluminosilicate zeolites, modified by reaction with an organic substituted silane, have been described jin U.S. Pat. No. 3,682,996 to Kerr and in U.S. Pat. No. 3,698,157 to Allen et al. The former of these patents describes, as novel compositions of matter, crystalline aluminosilicate esters made by reacting a crystalline aluminosilicate having an available hydrogen atom with an organic silane having a SiH group. The resulting compositions were disclosed as being catalysts useful for hydrocarbon processes, particularly hydrocracking. In the latter of the above patents, the use of ZSM-5 type crystalline aluminosilicate zeolites, modified by treatment with an organic-radical substituted silane are described, together with the use of such modified zeolites in chromotographic separation of the compounds contained in a C.sub.8 aromatic feed stock.
While the above-noted prior art is considered of interest in connection with the subject matter of the present invention, the catalyst, its manufacture and use in selectively producing low molecular weight olefins and/or para-xylene described herein has not, insofar as is known, been heretofore disclosed.
Low molecular weight olefins, i.e., ethylene and propylene, produced in accordance with the process described herein are valuable hydrocarbons and constitute building blocks from which many other commercially useful products can be manufactured. Of the xylene isomers, i.e., ortho-, meta- and para-xylene, the latter is of particular value being useful in manufacture of terephthalic acid which is an intermediate in the manufacture of synthetic fibers such as "Dacron". Mixtures of xylene isomers either alone or in further admixture with ethylbenzene, generally containing a concentration of about 24 weight percent para-xylene in the equilibrium mixture, have been previously separated by expensive superfraction and multistage refrigeration steps. Such process, as will be realized, has involved high operation costs and has a limited yield.